Slowing of acoustic waves in electrorheological and string-fluid complex plasmas

Abstract

The PK-4 laboratory consists of a direct current plasma tube into which microparticles are injected, forming a complex plasma. The microparticles acquire many electrons from the ambient plasma and are thus highly charged and interact with each other. If ion streams are present, wakes form downstream of the microparticles, which lead to an attractive term in the potential between the microparticles, triggering the appearance of microparticle strings and modifying the complex plasma into an electrorheological form. Here we report on a set of experiments on compressional waves in such a string fluid in the PK-4 laboratory during a parabolic flight and on board the International Space Station. We find a slowing of acoustic waves and hypothesize that the additional attractive interaction term leads to slower wave speeds than in complex plasmas with purely repulsive potentials. We test this hypothesis with simulations, and compare with theory.

Sound velocities of Lennard-Jones systems near the liquid-solid phase transition

“…For example, the presence of a long-range attractive (dipole-like) interaction can considerably suppress the sound velocity in complex plasma fluids (fluids composed of macroscopic charged particles immersed in a plasma environment). 53,54 The obtained results have been analysed in the context of the Lindemann's melting rule and Stokes-Einstein relation. The constancy of c l /v T and c t /v T is consistent with the functional form for the dependence of melting and freezing temperatures on density, which emerge in various theories and approximations.…”

Dust-Acoustic Nonlinear Waves in a Nanoparticle Fraction of Ultracold (2K) Multicomponent Dusty Plasma

“…According to our estimates (see below), the dust-acoustic velocity for the submicron dust fraction should significantly exceed the observed wave velocity (C d2 >> V). Such a low velocity of nonlinear dust-acoustic waves can be explained either within the framework of the model [ 49 ] (where the self-consistent charge of particles was taken into account), within the framework of research [ 50 ] (where dust compression waves in electrorheological dusty plasma were studied), or by the presence of submicron particle drift (second fraction particles).Under the considered experimental conditions, the drift hypothesis appears to be the most reasonable. It is important that the drift velocity of the second fraction particles should be approximately equal to the phase velocity of the waves.…”

Heat transport in a flowing complex plasma in microgravity conditions

“…7 , this difference was attributed to the formation of strings in the particle cloud. The strings tend to align themselves with the axis of discharge tube [23][24][25] and can reduce the viscosity of complex plasma. It is interesting to note that our result for kinematic viscosity of a 3D complex plasma is comparable to the lower end of the viscosity range of 0.6-7 mm 2 /s reported for 2D complex plasmas 3, 18,19,26,27 and also to that of liquid water 28 , ν w ≃ 1.8 mm 2 /s.…”